As shown in FIG. 30, a recording medium cartridge of a below-described type has been widely employed (for example, Japanese Patent Application Laid-Open No. hei 2-162275) as a recording medium cartridge 101. The recording medium cartridge 101 includes a disc 102, a shell (case) 103 in which the disc 102 is accommodated so as to rotate freely, a shutter 105 for opening and closing an opening part 104 for recording and reproducing data provided in the shell 103, and a shutter spring 106 for urging the shutter 105 to close the opening part 104. The shutter 105 is linearly moved relative to the shell 103 by the shutter spring 106 to open and close the opening part 104 for recording and reproducing data.
In the recording medium cartridge, the shutter 105 is linearly moved relative to the shell 103. Further, as shown in FIG. 31, a recording medium cartridge 201 of a type that a shutter 105 is rotated relative to a shell 103 to open and close an opening part 104 for recording and reproducing data has been developed (for example, Japanese Utility Model Application Laid-Open No. sho 61-57364).
In the recording medium cartridge 101 shown in FIG. 30, since the shutter 105 is moved linearly relative to the shell 103 to open and close the opening part 104 for recording and reproducing data, the opening part 104 for recording and reproducing data can be opened and closed with a small amount of movement. Accordingly, even when a torsion coil spring is employed for the shutter spring 106, the shutter 105 can be maintained assuredly in a closed state by the shutter spring 106.
On the contrary, in the recording medium cartridge 201 in which the shutter 105 is rotated relative to the shell 103 to open and close the opening part 104 for recording and reproducing data, when the spring force of a shutter spring 106 is exerted on the outer peripheral side of the shutter 105 to rotate the shutter 105 throughout a wide angle, the torsion coil spring as the shutter spring 106 is brought into what is called a completely opened state, as shown in FIG. 31, so that a resiliency is weakened. Thus, the shutter 105 is hardly maintained assuredly in a closed state.
The present invention provides a recording medium cartridge of a type that a shutter is rotated relative to a shell to open and close an opening part for recording and reproducing data in which the shutter can maintain assuredly the opening part for recording and reproducing data in a closed state.